Capacitor Dielectric Material?

[Roland PJ]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

Any comments welcomed
Regards
Roland

 

[Don Bruder]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

*HIGHLY* doutful, I'd say.

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

Any comments welcomed
Regards
Roland

Water in its *PURE* state is a nearly perfect insulator. SO the IDEA is
good. In practice, though...

Water with even a little contamination is anywhere from a medium-poor
conductor to better than a copper wire as a conductor, depending on the
type and quantity of contaminant.

Water-dielectric capacitors have been tried - and found wanting - by the
tesla coil types. They work great - ONCE. Generally, by the time the
second shot is ready to happen, the water has already been contaminated
enough by the metal plates leaching into it that it's worthless (or at
least lousy) as a capacitor, and the coil doesn't fire worth diddly.

On the other hand, there is the so-called "6-pack" capacitor - 6
long-neck bottles from your favorite brand of beer that comes in
straight-sided bottles. Wrap each one in tinfoil, as smooth and
wrinkle-free as humanly possible. Set them all on another sheet of
tinfoil, so that all of them are electrically connected. Now fill them
all with a saturated NaCl solution (AKA "Brine"), topped with an inch or
two of U.S.P Mineral Oil, then corked (usually with rubber stoppers).
Connect wires to 6 large nails, and drive the nails through the rubber
stoppers/corks, through the oil, and into contact with the brine. Run
the 6 wires together to a terminal. The other terminal is the sheet of
tinfoil the bottles are sitting on. Presto - One fairly large value
capacitor suitable for the high-voltage work involved with running a
Tesla coil - The tinfoil on the outside is one plate, the brine on the
inside is the other plate, the glass of the bottle is the dielectric.

 

[Roger Dewhurst]

*HIGHLY* doutful, I'd say.


Water in its *PURE* state is a nearly perfect insulator. SO the IDEA is
good. In practice, though...

Water with even a little contamination is anywhere from a medium-poor
conductor to better than a copper wire as a conductor, depending on the
type and quantity of contaminant.

Water-dielectric capacitors have been tried - and found wanting - by the
tesla coil types. They work great - ONCE. Generally, by the time the
second shot is ready to happen, the water has already been contaminated
enough by the metal plates leaching into it that it's worthless (or at
least lousy) as a capacitor, and the coil doesn't fire worth diddly.

On the other hand, there is the so-called "6-pack" capacitor - 6
long-neck bottles from your favorite brand of beer that comes in
straight-sided bottles. Wrap each one in tinfoil, as smooth and
wrinkle-free as humanly possible. Set them all on another sheet of
tinfoil, so that all of them are electrically connected. Now fill them
all with a saturated NaCl solution (AKA "Brine"), topped with an inch or
two of U.S.P Mineral Oil, then corked (usually with rubber stoppers).
Connect wires to 6 large nails, and drive the nails through the rubber
stoppers/corks, through the oil, and into contact with the brine. Run
the 6 wires together to a terminal. The other terminal is the sheet of
tinfoil the bottles are sitting on. Presto - One fairly large value
capacitor suitable for the high-voltage work involved with running a
Tesla coil - The tinfoil on the outside is one plate, the brine on the
inside is the other plate, the glass of the bottle is the dielectric.

--

I thought that you are supposed to use PET soft drink bottles.

R

 

[John Popelish]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

I think the term for this sort of material is artificial dielectric.
A Google search will turn up lots of hits.

 

[default]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

Any comments welcomed
Regards
Roland

Sounds doubtful. Energy is stored in the molecule/atoms of the
dielectric - they deform physically under an electrostatic field. -
the reason why some dielectrics are good at some frequencies and lossy
at others (dissipation factor changes with frequency) A conductor
introduced into the dielectric material might work - but because it
may serve to bring the plates closer together- effectively speaking -
and decrease the insulating ability of the dielectric - so it might
have to be thicker. zero gain

 

[Greg Hansen]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

Any comments welcomed
Regards
Roland

I'd wondered about just using an insulated metal plate as the
dialectric. But I analyzed it as two capacitors in series, and didn't
get the result I'd hoped for.

 

[Graboid]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

Pure water is also I think diamagnetic. What about deionized water?

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

Like a ferrite core? Ferrite is too hard to make.

An auto repair shop with a brake drum/disk grinder is a
good place to pick up some free iron filings. They could
be embedded in epoxy or fiberglass resion but it would not
be anywhere the same as ferrite.

What kind of voltages are you thinking about?
Some dilectrics work well only for certain voltage ranges.

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

What about trying some 'metal' cassette tape?

It's hard to control the property of liquid suspensions when
temperature is always moving things around. Try suspending
iron filings in gelatine or ...

Faraday wasn't recognized much for his academics.
If you want an exciting read, try his Experimental Researches
in Electricity. It gave me a great respect and inspiration for
actual experimentation. Then read Maxwell. There's an order
to the universe.

 

[Bob Eld]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

Any comments welcomed
Regards
Roland

I think your physics book has over simplified it. I don't belive that it is
a simple matter of "negating the voltage across the plates" but a case of
the distorion created in polar molecules by the electric field. That
distortion is a form of energy storage and has the effect of increasing the
capacitance which shows as high dielectric constant. Negating the voltage
implies some sort of conductor within the dialectric which is what you are
asking. But that's not the phenomenon so I doubt it would be successful.
Bob

 

[phaeton]

On the other hand, there is the so-called "6-pack" capacitor - 6
long-neck bottles from your favorite brand of beer that comes in
straight-sided bottles. Wrap each one in tinfoil, idd> for more info

Do you have ANY idea how difficult it will be for me to build this once
I empty those 6 bottles of Tyranena Porter? I probably shouldn't be
playing with tesla coils, either.


-phaeton

 

[default]

Do you have ANY idea how difficult it will be for me to build this once
I empty those 6 bottles of Tyranena Porter? I probably shouldn't be
playing with tesla coils, either.


-phaeton

Yes, I do.

I'm on homebrew porter myself. Real men and all . . .

 

[phaeton]

Yes, I do.

I'm on homebrew porter myself. Real men and all . . .

Oh... if only I had a basement :-(

 

[default]

Do you have ANY idea how difficult it will be for me to build this once
I empty those 6 bottles of Tyranena Porter? I probably shouldn't be
playing with tesla coils, either.


-phaeton

Glass plate caps with aluminum flashing for plates and 3/32" picture
frame glass work just fine - pot in wood boxes with paraffin - a
single homemade (layered - low ESR) cap across lots of commercial
units will make a Tesla coil get hopping.

Really? drinking beer to make caps? Well, I can't be too critical. I
drank two cases of "Carling Black Label" (only beer we had in all
steel cans - $2.60 - 24 can cases) to build an antenna. In my Navy
days.

 

[default]

Oh... if only I had a basement :-(

I don't have a basement, and live in a warm climate. I brew in
October, through June. I do 18 cases a year plus whatever I consume
while brewing.

Where do you live? Dig a "root cellar?" I've been toying with that
idea - hurricane protection, and a great wine cellar - and what better
way to wait out a hurricane (unless the water starts creeping up in
the cellar) Life is rough - don't fight it.

 

[phaeton]

I don't have a basement, and live in a warm climate. I brew in
October, through June. I do 18 cases a year plus whatever I consume
while brewing.

Where do you live? Dig a "root cellar?" I've been toying with that
idea - hurricane protection, and a great wine cellar - and what better
way to wait out a hurricane (unless the water starts creeping up in
the cellar) Life is rough - don't fight it.

I live in Wisconsin.

I've read up a bunch on it, but many articles talk about doing stuff
the 'right' way, I'm curious as to how feasible doing it 'my' way would
be.

I'd like to talk more about this with ya, but I don't want to hijack
the OPs topic ;-) Want to drop emails or start a different topic
somewhere else?

-phaeton

 

[default]

I live in Wisconsin.

I've read up a bunch on it, but many articles talk about doing stuff
the 'right' way, I'm curious as to how feasible doing it 'my' way would
be.

I'd like to talk more about this with ya, but I don't want to hijack
the OPs topic ;-) Want to drop emails or start a different topic
somewhere else?

-phaeton

Sure, of course.

email:ganeth/at/movemail/dot/com Slashes to dots and @

I'm in North Carolina and have been brewing since 92.

 

[default]

I'd wondered about just using an insulated metal plate as the
dialectric. But I analyzed it as two capacitors in series, and didn't
get the result I'd hoped for.

Water (very pure de ionized) would seem to be a good dielectric. but
DI water has this habit of finding ions from anything (even plastic)
so you'd probably end up circulating the water and introducing fresh
DI.

I know a lab where they used DI water and the CATION, and ANION resin
(beds) tanks were close to the spigots - for months they tried to
convince me they were in dire danger from electrocution because of the
wiring. I could never measure anything with my meters. I remembered
this old Scientific American article on building a static electricity
generator from just a big tank spraying water . . . added a grounded
brass nozzle to their plastic spigot and they were happy.

 

[default]

I think your physics book has over simplified it. I don't belive that it is
a simple matter of "negating the voltage across the plates" but a case of
the distorion created in polar molecules by the electric field. That
distortion is a form of energy storage and has the effect of increasing the
capacitance which shows as high dielectric constant. Negating the voltage
implies some sort of conductor within the dialectric which is what you are
asking. But that's not the phenomenon so I doubt it would be successful.
Bob

Yeah

Apply an electrostatic field and the molecules and electron orbits
distort. That distortion stores more energy than a vacuum would.
Discharge the cap, and the stored energy (all those bent up electrons)
is given up in the form or electron flow. How fast a particular
compound will release the energy is a matter of dissipation factor.

OR, from an AC perspective:

In addition to pure electron attraction manipulating the dielectric
compounds - there are mechanical considerations as well - resonance of
the molecules in the dielectric. Just like MRI machines - excite a
dielectric and it responds at its own pace. A dielectric that will be
efficient at 10 MHZ might not at 20 MHz - Most dielectrics that are
efficient (less dissipated heat) at low frequencies will be good at
high frequencies - BUT NOT ALL - so you look at the specs for the
frequency you are using, or check a chart that covers your freq. or
check the manufacturer's specs. Same thing with microwave ovens.

Maynard Fergusen died. Damn

 

[Michael A. Terrell]

Where do you live? Dig a "root cellar?" I've been toying with that
idea - hurricane protection

That's just plain silly! Hurricanes don't need protection. ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[jasen]

Hi

I have a question (mainly of academic interest) about capacitors.

I read in my physics text book that polar substances such as water have
a much higher dielectric constant (K) than vacuum because the polar
molecules align so as to negate the voltage across the plates.

So, could you get the same effect with a dielectric comprising small
bits of conductor (e.g. iron filings or graphite powder) embedded in an
insulator (oil, clay, whatever)?

It seems to me that the small pieces of conductor would polarize
similarly to the molecular polarization of water, but maybe better.

It'd work, but would it help. the particles would reduce the effective
thickness of the dielectric and that'd reduce the breakdown voltage.

If the particles are mobile they could move by electrostatic attraction to
short-circuit the capacitor.

This is the sort of thing you can play with in an electrostatics lab.

Bye.
Jasen